1. Preheat your oven to 375°F (190°C). This temperature is perfect for baking the sausage thoroughly while melting the cheese to that beautiful golden finish.
2. Heat olive oil in a large skillet over medium heat. Add the sliced onions and cook until soft and translucent, about 5 minutes. This step brings out the natural sweetness that complements the sausage beautifully.
3. Add the minced garlic and cook for another minute, just until fragrant. Be careful not to burn it—garlic can turn bitter quickly.
4. Remove the onions and garlic from the skillet and set aside. In the same skillet, add the sausage, breaking it up with a wooden spoon. Cook until browned and cooked through, about 7-8 minutes. I always like to brown the sausage well—it adds so much depth to the dish.
5. Return the onions and garlic to the skillet with the sausage. Stir in the dried oregano and crushed red pepper flakes if using. Mix well to combine all those savory flavors.
6. Spread the marinara sauce evenly in the bottom of a baking dish (around 9×9 inches). This layer keeps the sausage moist and infuses it with a rich tomato flavor.
7. Pour the sausage mixture over the marinara sauce and spread it out evenly.
8. Sprinkle the shredded mozzarella and provolone cheeses evenly over the sausage mixture. Then, finish with a generous dusting of Parmesan cheese on top. The combination of cheeses melts into a creamy, bubbly blanket that’s utterly irresistible.
9. Bake uncovered for 20-25 minutes, or until the cheese is melted and golden brown. You’ll know it’s ready when the edges are bubbly and slightly crisp.
10. Let the dish rest for 5 minutes before serving. This resting time helps everything set and makes serving easier.

One of my fondest memories is making this dish with my daughters, who love sprinkling the cheese on top just right—little moments like these are what make cooking so special.